The invention relates to a dispenser having a container whereof one end is sealed by a sealing piston which, in relation to the container, is adjustable in a first direction, wherein there is arranged, on the side of the sealing piston remote from a product chamber of the container, a spreading spring which is in engagement with the inner wall of the container and prevents movement of the sealing piston in a second direction which is opposed to the first direction.
A dispenser of this kind is also known, in connection with toothpaste, as a tube dispenser; however, the invention is not restricted to this but is also applicable to other viscous products or products to be metered using a dispenser.
However, in the text below a tube dispenser for toothpaste will be taken as the starting point, by way of example.
The dispenser has a container which is of cylindrical shape, conventionally based on a circle or based on an oval, and at the upper end whereof a pump-type removal device is constructed. The toothpaste is accommodated in the interior of the container, which forms a product chamber, and at the lower end of the container an axially displaceable sealing piston is inserted into it. On the side of the sealing piston remote from the product chamber there is seated a spreading spring which is connected to the closure piston and is supported against the inner wall of the container or is in engagement with this inner wall.
The toothpaste is conveyed outwards by expulsion, and when or after the removal device is deactivated a negative pressure is generated in the product chamber, on the basis whereof the sealing piston is displaced axially in the container by a small amount until the volume of the product chamber has been reduced enough for pressure to be equalized.
The purpose of the spreading spring is to prevent the sealing piston from being displaced in the opposing direction, that is to say in the direction of the lower end of the container. When the sealing piston is displaced as a result of the negative pressure prevailing in the product chamber, it draws the spreading spring with it, and the latter then comes briefly out of engagement, or into less engagement, with the inner wall of the container. As soon as movement of the piston has changed, the spreading spring abuts against the inner wall of the container again, as a result of its intrinsic elasticity.
The spreading spring takes the form of a metal part which has to be manufactured beforehand and then mounted on the sealing piston, which is conventionally made from synthetic material. This procedure is complex and cost-intensive.
There is also a risk that children or inattentive users will reach into the container from below and injure themselves on the spreading spring there. For this reason, a cover is conventionally provided by means of which the container is sealed at its lower end. The manufacture and subsequent mounting of this cover further increases the cost of the dispenser.
The object of the invention is to provide a dispenser of the type mentioned that can be manufactured simply and at low cost.